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A semiconductor device that is used to detect the DNA makeup of a human cell. DNA chains comprise molecules that pair with each other, and micro arrays contain millions of DNA strands designed to mate with their other half as the liquefied human cells are poured over them. This "hybridization" process is then detectable by a laser.

Micro arrays are revolutionizing medicine by being able to pinpoint a very specific disease or the susceptibility to it. Sometimes called "biochips," Affymetrix (www.affymetrix.com) pioneered this technology with its GeneChip family. See Human Genome Project.

Micro Array Features

The square locations on this Affymetrix array are called "features," and each feature holds millions of identical DNA strands called "probes." The probes are built like semiconductor chips, one layer at a time. (Image courtesy of Affymetrix.)

Hybridization (Pairing)

The human DNA sample, which has been replicated millions of times and fragmented into short pieces, is washed over the micro array. The red balls depict biotin molecules that were adhered to the fragments, which "swim" around the probes for up to 16 hours. During that time, some strands will pair with the probes (the hybridization process). (Image courtesy of Affymetrix.)

Detection

The array is rinsed and washed with a fluorescent stain that clings to the biotin on the strands of the human sample that remain. A laser causes them to glow, and the DNA is analyzed (genotyped) based on which probes on the array they mated with. (Images courtesy of Affymetrix.)